KR20120102507A - Process for partial shrinkage compensation in plastics mouldings - Google Patents

Abstract

PURPOSE: A method for correcting the local shrinkage of a plastic product is provided to enable to apply for an operation device which a user can see with a back-lighting even in a dark place. CONSTITUTION: A method for correcting the local shrinkage of a plastic product comprises next steps. One surface of a plastic film is rearward-injected with greater than one kind of a thermoplastic plastic while not rearward-injecting one or more partial portions of a plastic film. An obtained plastic is cooled. A portion where not being rearward-injected of the obtained plastic product can be heated again.

Description

Method for Compensation for Partial Shrinkage of Plastic Molds {PROCESS FOR PARTIAL SHRINKAGE COMPENSATION IN PLASTICS MOULDINGS}

The present invention relates to a method for producing a plastic molding in which partial shrinkage compensation has been performed, and to a plastic molding produced by the method.

For example, in the manufacture of parts where partial transparency is desired in finished parts, such as in an operation console of an automobile part with an actuating button made visible to the user in the dark by partial backlighting, a randomly printed plastic film is windowed. Back-injection into thermoplastics by means of the state-of-the-art. The method of back-injecting a plastic film into thermoplastic by an injection-molding method is called film insert molding (FIM). The so-called window technique offers the opportunity to cover the area that is later back-lit with a die or slider, so that there is no thermoplastic material in that area.

However, the method suffers from the problem that, in the treatment of thermoplastics by the injection-molding method, the parts shrink on cooling but the film in the non-back-injected zone does not shrink at the same time. As a result, bulges or dents occur in such areas, which results in noticeable non-flatness of the surface of the part.

Up to now, the problem has been to use a glass fiber to fill the thermoplastic for back-injection (because the shrinkage of the plastic material can be reduced accordingly) or to prevent the formation of bulge or dents By using However, it has not been possible to completely eliminate the problem by either of the two above without further problems occurring simultaneously in terms of end use. Using glass fibers as an additional filler not only entails additional material costs and additional expenditures in terms of the device during processing of the filled plastic composition, but also increases tool wear. In addition, in many cases the formation of bulges or dents can be reduced but not completely prevented by this method. In addition to the additional foil costs for larger foil thicknesses, the use of thicker plastic films, especially when the film is also further printed, reduces its light transmission and requires a stronger light source for proper back-writing. In addition, the part is stressed in the non-back-jecting zone, which carries the risk of cracking or cracking in that zone.

Therefore, there was a need to provide a method for producing a part that is partially transparent in the finished part and which does not exhibit the disadvantages mentioned above.

Accordingly, the object underlying the present invention is to find a method for manufacturing a part where partial transparency is desired in the finished part. In particular, the formation of bulges or dents in the finished part should be prevented without allowing additional material costs. In addition, the light transmission of the part in the back-lit region should be as high as possible so that the back-writing is possible even with a weak energy-saving light source.

Surprisingly, this object has been achieved by a method of producing a plastic molding in which an optionally printed plastic film is back-injected into thermoplastics over a part of its surface and after cooling, post-shrinkage by at least partial heating.

Accordingly, the present invention provides a method for producing a plastic molding, wherein

A) back-injecting one side of the plastic film with one or more thermoplastics, without back-injecting one or more partial regions of the plastic film,

B) cool the plastic molding obtained in step A),

C) then, at least, again heating the non-injected zone of the plastic molding obtained in step B).

The bulge or dent of the non-back-jected zone can be completely removed by the method according to the invention. The method according to the invention offers the possibility of using thin plastic films with good light transmission, which can be back-lit even with a weak light source without requiring additional fillers to reduce the shrinkage of the thermoplastics. A further advantage of the method according to the invention is that the part is not stressed in the area that is not post-injected, so there is no risk associated with cracking or cracking in this area.

The plastic film used in step A) can be printed or colored on one or both sides with colorants or pigments. Preferably, the plastic film used in step A) is printed on one side. When a plastic film printed on one side is used in step A), it can be back-injected with thermoplastics on the printed side or non-printed side. When back-injection is carried out on the printed side, thermally stable printing inks are particularly suitable for printing, as described, for example, in WO-A 2009/138217.

In a preferred embodiment of the process according to the invention, the plastic film used in step A) is formed. Such molding can be carried out before or after possible printing, but preferably after printing possible by methods known to those skilled in the art. Examples of possible formation methods that may be mentioned are mechanical molding, hydroforming and high pressure forming (HPF) methods. For example, the high pressure forming method described in WO-A 2009/043539 or EP-A 371 425 is preferred.

At least in step C), the non-back-jected zone of the plastic molding obtained in step B) is heated at least to a temperature at which shrinkage and / or shrinkage of the plastic film of the non-back-fired zone can be achieved. do. Preferably, at least in the step C), the non-backjected zone of the plastic molding obtained in step B) is at least at a temperature in the region above the temperature of 70 ° C. below the glass transition temperature T _g , preferably of the plastic film. Temperature in the region above 50 ° C. below the glass transition temperature T _g of the plastics material, in other words, at a temperature in excess of T _g minus 70 ° C. of the plastics material of the plastic film (at least, in the region above T _g -70 ° C.). Temperature), preferably at least to a temperature above T _g minus 50 ° C. (at least in the region above T _g -50 ° C.). In a preferred embodiment, step C), at least the back of the plastic molded article obtained in step B) from - the area that is not emitted at least, low 50 ℃ than the glass transition temperature of the plastic material of the plastic film T _g than the glass transition temperature T _g Heat to a high range of 50 ° C. Preferably, the heating in step C), at least 40 ℃ lower than the glass transition temperature of the plastic material of the plastic film T _g is performed at a temperature of 40 ℃ high range above the glass transition temperature T _g. In a preferred embodiment of the invention, the heating in step C) is carried out at a temperature of at least 10 ° C. below the glass transition temperature T _g and 40 ° C. above the glass transition temperature T _g of the plastic material of the plastic film. Very particularly preferably, performing heating at a temperature of at least, greater than the glass transition temperature T _g in the specified range of the plastic material of the plastic film, the glass transition temperature exceeds T _g. Very particular preference is given to temperatures in which the glass transition temperature T _g of the plastics material of the plastic film exceeds at most 50 ° C, preferably at most 40 ° C. If the plastic film contains at least one polycarbonate or copolycarbonate, the non-back-jetted zone is at least, preferably above 60 ° C., particularly preferably above 70 ° C., very particularly in step C). Preferably it is heated to a temperature above 100 ° C.

The glass transition temperature T _g is determined by differential scanning calorimetry (DSC) according to standard ISO 113557-2 at a heating rate of 10 K / min, defining T _g as the mid-point temperature (tangent method).

The temperature at which the non-injected zone of the plastic molding obtained in at least step B) is heated in step C) can be measured, for example, with a commercial infrared camera, preferably a commercial infrared line camera for non-contact temperature measurement. For example, a corresponding infrared camera from Bartec Messtechnik und Sensorik, such as, for example, line pyrometer or Dias Infrared GmbH from Bartec Mestech und Zenzorik. GmbH's infrared line cameras are suitable for this purpose.

Preferably, the non-backjected zone of the plastic molding obtained in step B) is less than 60 seconds, preferably less than 20 seconds, particularly preferably less than 15 seconds, very particularly preferred at the temperatures mentioned in step C) Preferably for less than 10 seconds. In particular as short a time as possible in relation to the reasons of process efficiency and the temperature load of the plastic material is preferred and advantageous. However, it is also possible to heat the non-backjected zone of the plastic molding obtained in step B) at the temperature (s) mentioned for a long time.

The heating in step C) can be carried out in any suitable form of heat supply. Heating can be carried out in part over the entire surface of the non-back-jected and surrounding areas or parts. There may also be a preferred possibility of any of the above mentioned alternatives. Heating can be performed both inside the injection-molding tool and outside the injection-molding tool. Inside the injection-molding tool, for example, the supply of heat by means of a ceramic heating element is possible. Outside the injection-molding tool a supply of heat is possible, for example by means of an IR emitter or hot air.

After heating again in step C), the obtained plastic molding is cooled. Preferably, the cooling is carried out at a temperature below 50 ° C., particularly preferably below 40 ° C. and very particularly preferably below 30 ° C.

Preferably, the plastic film used in step A) has a thickness of 50 μm to 500 μm, particularly preferably 75 μm to 400 μm and very particularly preferably 100 μm to 300 μm.

The plastic film used in step A) is a plastic film containing at least one thermoplastic, particularly preferably a plastic film consisting essentially of at least one thermoplastic and a conventional plastic additive.

Suitable thermoplastics for plastic films and thermoplastics for back-injection are thermoplastic plastics selected from polycondensation products of polymers and / or difunctional reactive compounds of ethylenically unsaturated monomers, independently of one another.

Particularly suitable thermoplastics are polycarbonates or copolycarbonates based on diphenols, poly- or copoly-acrylates and poly- or copoly-methacrylates such as, for example, preferably, Polymethyl methacrylate, a polymer or copolymer with styrene, such as, for example, preferably, transparent polystyrene, polystyrene acrylonitrile (SAN) or acrylonitrile-butadiene-styrene copolymer (ABS), transparent thermoplastic poly Polyurethanes as well as polyolefins such as, for example, preferably polyolefins based on transparent polypropylene type or cyclic olefins (e.g. TOPAS ^® , Hoechst), poly- or cobalt of terephthalic acid Poly-condensation products, such as, for example, preferably poly- or copoly-ethylene terephthalates (PET or CoPET), glycol-modified PET (PETG) or poly- or copolybutylene terephthalate (PBT or CoPBT) or mixtures of those mentioned above.

In particular polycarbonates or copolycarbonates having an average molecular weight M _w of 500 to 100,000, preferably 10,000 to 80,000, particularly preferably 15,000 to 40,000, or at least one such polycarbonate or copolycarbonate Very particular preference is given to blends containing nates. At least one poly- or copoly-condensation product of the aforementioned polycarbonates or copolycarbonates with terephthalic acid, in particular at least one of terephthalic acid having an average molecular weight M _w of 10,000 to 200,000, preferably 26,000 to 120,000 Further preference is given to blends with poly- or copoly-condensation products. In a particularly preferred embodiment of the invention, the blend is a blend of polycarbonate or copolycarbonate with poly- or copoly-butylene terephthalate. Such blends of polycarbonates or copolycarbonates with poly- or copolybutylene terephthalates are preferably from 1 to 90% by weight of polycarbonates or copolycarbonates and from 99 to 10% by weight It may be a blend containing% poly- or copoly-butylene terephthalate, preferably 1 to 90% by weight polycarbonate and 99 to 10% by weight polybutylene terephthalate, the sum of said amounts Is 100% by weight. Particularly preferably, these blends of polycarbonates or copolycarbonates with poly- or copolybutylene terephthalate are 20 to 85% by weight of polycarbonates or copolycarbonates and 80 to 15% by weight of poly- or copolybutylene terephthalate, preferably a blend containing 20 to 85% by weight of polycarbonate and 80 to 15% by weight of polybutylene terephthalate, said amount The total of is 100% by weight. Very particularly preferably, such blends of polycarbonates or copolycarbonates with poly- or copolybutylene terephthalates comprise 35 to 80% by weight of polycarbonates or copolycarbonates and 65 It may be a blend containing from 20 to 20% by weight of poly- or copoly-butylene terephthalate, preferably 35 to 80% by weight of polycarbonate and 65 to 20% by weight of polybutylene terephthalate, The sum of the amounts is 100% by weight.

In a preferred embodiment, the aromatic polycarbonates or copolycarbonates are particularly suitable as polycarbonates or copolycarbonates.

Polycarbonates or copolycarbonates can be linear or branched in a known manner.

The preparation of these polycarbonates can be carried out in a known manner from diphenols, carbonic acid derivatives, optionally chain terminators and optionally branching agents. Details of polycarbonate preparation have been published in many patent specifications for about 40 years. See, eg, Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Volume 9, Interscience Publishers, New York, London, Sydney 1964, to D. Freitag U. Grigo, P.R. Mueller, H. Nouvertne ', BAYER AG, "Polycarbonates" in Encyclopedia of Polymer Science and Engineering, Volume 11, Second Edition, 1988, pages 648-718 and finally Drs. U. Grigo, K. Kirchner and P.R. Mueller "Polycarbonate" in Becker / Braun, Kunststoff-Handbuch, Volume 3/1, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag, Munich, Vienna 1992, pages 117-299.

Suitable diphenols can be, for example, dihydroxyaryl compounds of formula (I).

<Formula I>

Wherein Z is an aromatic radical having 6 to 34 carbon atoms and which may contain one or more optionally substituted aromatic nuclei and aliphatic or cycloaliphatic radicals or alkylaryl or heteroatoms as crosslinking members.

Particularly preferred dihydroxyaryl compounds are resorcinol, 4,4'-dihydroxydiphenyl, bis- (4-hydroxyphenyl) -diphenyl-methane, 1,1-bis- (4-hydroxyphenyl ) -1-phenyl-ethane, bis- (4-hydroxyphenyl) -1- (1-naphthyl) -ethane, bis- (4-hydroxyphenyl) -1- (2-naphthyl) -ethane, 2,2-bis- (4-hydroxyphenyl) -propane, 2,2-bis- (3,5-dimethyl-4-hydroxyphenyl) -propane, 1,1-bis- (4-hydroxyphenyl ) -Cyclohexane, 1,1-bis- (3,5-dimethyl-4-hydroxyphenyl) -cyclohexane, 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethyl- Cyclohexane, 1,1'-bis- (4-hydroxyphenyl) -3-diisopropyl-benzene and 1,1'-bis- (4-hydroxyphenyl) -4-diisopropyl-benzene.

Very particularly preferred dihydroxyaryl compounds are 4,4'-dihydroxydiphenyl, 2,2-bis- (4-hydroxyphenyl) -propane and 1,1-bis- (4-hydroxyphenyl)- 3,3,5-trimethyl-cyclohexane.

Very particularly preferred copolycarbonates include 1,1-bis- (4-hydroxyphenyl) -3,3,5-trimethyl-cyclohexane and 2,2-bis- (4-hydroxyphenyl) -propane Can be prepared.

Suitable carbonic acid derivatives can be, for example, diaryl carbonates of the general formula (II).

&Lt;

Wherein R, R 'and R "may be the same or different and independently of one another hydrogen, linear or branched C ₁ -C ₃₄ -alkyl, C ₇ -C ₃₄ -alkylaryl or C ₆ -C ₃₄ -Aryl, R may further represent -COO-R '''whereinR''' is hydrogen, linear or branched C ₁ -C ₃₄ -alkyl, C ₇ -C ₃₄ -alkyl Aryl or C ₆ -C ₃₄ -aryl.

Particularly preferred diaryl compounds are diphenyl carbonate, 4-tert-butylphenyl-phenyl carbonate, di- (4-tert-butylphenyl) carbonate, biphenyl-4-yl-phenyl carbonate, Di- (biphenyl-4-yl) carbonate, 4- (1-methyl-1-phenylethyl) -phenyl-phenyl carbonate, di- [4- (1-methyl-1-phenylethyl)- Phenyl] carbonate and di- (methylsalicylate) carbonate.

Very particular preference is given to diphenyl carbonate.

Both diaryl carbonates and different diaryl carbonates can be used.

It is further possible to use, as chain terminator, one or more monohydroxyaryl compound (s) that have not been used, for example, in the preparation of the diaryl carbonate (s) used to control or change the end groups. . Such compound may be of formula III.

<Formula III>

Where

R ^A is linear or branched C ₁ -C ₃₄ -alkyl, C ₇ -C ₃₄ -alkylaryl, C ₆ -C ₃₄ -aryl or -COO-R ^D , wherein R ^D is hydrogen, linear or branched C ₁ -C ₃₄ -alkyl, C ₇ -C ₃₄ -alkylaryl or C ₆ -C ₃₄ -aryl,

R ^B , R ^C may be the same or different and independently of one another represent hydrogen, linear or branched C ₁ -C ₃₄ -alkyl, C ₇ -C ₃₄ -alkylaryl or C ₆ -C ₃₄ -aryl.

Preference is given to 4-tert-butylphenol, 4-isooctylphenol and 3-pentadecylphenol.

Suitable branching agents may be compounds having three or more functional groups, preferably compounds having three or more hydroxyl groups.

Preferred branching agents are 3,3-bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2,3-dihydroindole and 1,1,1-tri- (4-hydroxyphenyl)- It's ethane.

In a preferred embodiment of the invention, suitable poly- or copoly-condensation products of terephthalic acid are polyalkylene terephthalates. Suitable polyalkylene terephthalates are, for example, reaction products of aromatic dicarboxylic acids or their reactive derivatives (eg dimethyl esters or anhydrides) and aliphatic, cycloaliphatic or araliphatic diols and mixtures of these reaction products.

Preferred polyalkylene terephthalates can be prepared by known methods from terephthalic acid (or reactive derivatives thereof) and aliphatic or cycloaliphatic diols having from 2 to 10 carbon atoms (Kunststoff-Handbuch, Vol. VIII, p. 695 ff, Karl-Hanser-Verlag, Munich 1973].

Preferred polyalkylene terephthalates are at least 80 mol%, preferably at least 90 mol%, based on the dicarboxylic acid component, and at least 80 mol%, preferably at least 90 mol%, based on the diol component. Ethylene glycol and / or 1,4-butanediol radicals.

Preferred polyalkylene terephthalates are, in addition to terephthalic radicals, radicals of other aromatic dicarboxylic acids having from 8 to 14 carbon atoms or aliphatic dicarboxylic acids having from 4 to 12 carbon atoms, for example phthalic acid, Up to 20 mole percent of radicals of isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid and cyclohexanediacetic acid It may contain.

In addition to ethylene glycol and 1,4-butanediol radicals, preferred polyalkylene terephthalates are other aliphatic diols having 3 to 12 carbon atoms or cycloaliphatic diols having 6 to 21 carbon atoms, for example 1,3- Propanediol, 2-ethyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, cyclohexane-1,4-dimethanol, 3-methyl-2,4- Pentanediol, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol and 2-ethyl-1,6-hexanediol, 2,2-diethyl-1,3 -Propanediol, 2,5-hexanediol, 1,4-di-([beta] -hydroxyethoxy) -benzene, 2,2-bis- (4-hydroxycyclohexyl) -propane, 2,4 -Dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2-bis- (3- [beta] -hydroxyethoxyphenyl) -propane and 2,2-bis- (4- It may contain up to 20 mole% of the radicals of hydroxypropoxyphenyl) -propane (see DE-OS 24 07 674, 24 07 776, 27 15 932).

Polyalkylene terephthalates are branched by incorporating relatively small amounts of trivalent or tetravalent alcohols or tribasic or tetrabasic carboxylic acids, as described, for example, in DE-OS 19 00 270 and US-PS 3 692 744. Can be mad. Examples of preferred branching agents are trimesic acid, trimellitic acid, trimethylol-ethane and -propane and pentaerythritol.

Preferably, up to 1 mol% branching agent is used based on the acid component.

Particular preference is given to polyalkylene terephthalates prepared from only terephthalic acid and its reactive derivatives (eg dialkyl esters thereof) and ethylene glycol and / or 1,4-butanediol, and mixtures of such polyalkylene terephthalates.

Preferred polyalkylene terephthalates are also copolyesters prepared from at least two of the aforementioned acid components and / or at least two of the aforementioned alcohol components, particularly preferred copolyesters being poly (ethylene glycol / 1, 4-butanediol) terephthalate.

Polyalkylene terephthalates which are preferably used as components have an inherent viscosity of approximately 0.4 to 1.5 dl / g, preferably 0.5 at 25 ° C. in each case in phenol / o-dichlorobenzene (1: 1 parts by weight). To 1.3 dl / g.

In a preferred embodiment of the process according to the invention, the plastic film contains at least one polycarbonate or copolycarbonate.

In a preferred embodiment of the process according to the invention, the thermoplastic is at least one polycarbonate or copolycarbonate, polyacrylate or copolyacrylate, poly (meth) acrylate or copoly (meth) acrylic Acrylate or acrylonitrile-butadiene-styrene copolymer (ABS).

In order that one or more partial regions of the plastic film are not back-injected, the area of the plastic film which is not to be back-injected is preferably covered with one or more dies or sliders in step A).

In a preferred embodiment of the method according to the invention, the back-injected partial region (s) of the plastic film is completely surrounded by the back-injected partial region of the plastic film after back-injection. In a particularly preferred embodiment of the method according to the invention, the plurality of non-contiguous partial regions of the plastic film are not back-injected in step A) and the non-back-injected partial regions of the plastic film are plastic after the back-injection. It is completely surrounded by the back-projected partial area of the film.

The back-injection in step A) is preferably carried out by a window technique. It is known to those skilled in the art to cover the area of the plastic film which is not to be back-jected with one or more dies or sliders in step A) so that one or more partial areas of the plastic film are not back-ejected.

Back-injection of the plastic film is carried out by methods known to those skilled in the art. For example, a plastic film can be placed on the first half of the open injection-molding tool for this purpose, so that a cavity (gap, hollow space) is formed between the film and the second tool half, The tool can be closed by applying the second half of the tool to the first half, and then back-injecting the plastic film in the tool into the thermoplastic by introducing the thermoplastic into the cavity. The die or slider used to cover the area that will not be post-injected can thus preferably be secured to the second half of the tool and cover the area that should be kept blank when the tool is closed.

If a plastic film printed on one side is used in step A), it can be arranged with the first tool half so that the printed side faces the wall of the tool or the printed side faces away from the wall of the tool.

After back-injection, the tool is opened after part or all cooling in step B). Step C) can then be carried out on one of the two tool halves after the tool is opened. Alternatively, it is also possible to remove the plastic molding from the tool after cooling in step B) and to perform step C) outside the tool. The plastic molding can also be removed from the tool before the intended complete cooling can be achieved and cooling can be carried out outside the tool. For example, the procedure may be advantageous in some embodiments of the invention if sufficient shrinkage of the molding obtained in step A) cannot be achieved in step B) or due to sufficient tool temperature remaining, or can be achieved quickly enough. Can have

The cooling in step B) of the plastic molding obtained in step A) before heating again in step C) is preferably carried out at a temperature at which complete shrinkage and / or shrinkage of the plastic molding obtained in step A) can occur. . The cooling in step B) of the plastic molding obtained in step A) before heating again in step C) is preferably at a temperature below 60 ° C, particularly preferably below 50 ° C and very particularly preferably below 40 ° C. Is performed. It is further preferred that the plastic molding obtained in step A) is not subcooled in step B) before it is heated again in step C), that is to say that it is not cooled to a temperature below 0 ° C., preferably below 10 ° C. Further preferred. In a preferred embodiment, the cooling in step B) of the plastic molding obtained in step A) before heating in step C) is carried out at room temperature, with room temperature being between 15 and 25 ° C., in particular 23 ° C., within the context of the invention. It is understood as the temperature of.

In the non-back-jecting zone, preferably at least a partial area of the plastic film is transparent or translucent, ie light transmissive, allowing back-lighting in said transparent or translucent area. The plastic film may be 100% light transmissive to light in the visible wavelength range in at least a partial region of the non-back-projected zone, preferably the plastic film is translucent in at least a partial region of the non-back-projected zone . Within the context of the present invention, translucent is understood to be light transmissive in the visible wavelength range of more than 20% and less than 100%, preferably more than 50% and less than 100%, particularly preferably more than 70% and less than 100%. Should be. The visible wavelength range of light spans the wavelength range of 380-780 nm. Light transmittance can be measured using Hunter UltraScanPRO using diffusion / 8 ° geometry.

However, it is also possible for the plastic film to be neither transparent nor translucent in at least a partial region of the non-back-jected zone for producing operating elements, for example accessible capacitive switches or mechanical switches.

The invention further provides a plastic molding obtainable by the process according to the invention.

The plastic moldings produced by the process according to the invention are for example electronic devices, household devices, mobile phones, computers, for example computer keyboards, vehicle interiors, for example automotive interiors and aircraft or Suitable for use in railway car interior materials. Plastic moldings produced by the process according to the invention can be used in applications such as actuating elements accessible to the user even in the dark, for example by back-writing.

1 to 5 describe in schematic form the production of a plastic molding according to the invention in the form of a window technique.
1 shows a plastic film 2 disposed on the tool half 1 of an open injection-molding tool. The die 4 is fixed to the second tool half 3 to cover the non-back ejection area.
FIG. 2 shows a closed injection-molding tool containing a plastic film 2, with the die 4 fixed to the second tool halves 3 defining a non-back ejection area of the plastic film 2 of the tool. It is covered inside.
3 shows a closed injection-molding tool, wherein the plastic film 2 is back-injected into the thermoplastic 5 in a region not covered by the die 4.
4 shows an open injection-molding tool from which the plastic molding 6 was removed after cooling.
FIG. 5 shows the cutout 7 of the plastic molding 6 removed from the injection-molding tool after cooling, with the bulge in the non-injection zone being visible (see (a)). FIG. 5 further shows how the bulge is removed by heating according to the invention (see (b)) and how a flat surface is achieved in the non-back-jecting zone (see (c)).

The following examples are intended to illustrate the invention by way of example and should not be construed as limiting.

Example

Three polycarbonate films (Makrofol ^® DE) (glass transition temperature T _g : 145 ° C.) with various thicknesses of 150 μm, 175 μm and 200 μm and polycarbo having a layer thickness of 375 μm carbonate / polybutylene terephthalate blend films (Bay pole (Bayfol) ^® CR) (glass transition temperature T _g: 125 ℃) of which was pre-printed with a screen printing ink. Noriphan ^® HTR was used as the screen printing ink.

The glass transition temperature in each case is defined by differential scanning calorimetry (DSC) according to standard ISO 113557-2 at a heating rate of 10 K / min, defining T _g as the mid-point temperature (tangent method) in the second heating operation. T _g was measured.

Then, the polycarbonate film carbonate injection-molding in a thermoplastic polycarboxylic carbonate back to (Mark rolron (Makrolon) ^® 2405) - and injection. Polycarbonate / polybutylene terephthalate blend films injection-molding tool in the back of a thermoplastic polycarbonate / ABS blend (Blend bay (Bayblend) ^® T65) - and injection. The test was performed on an Arburg Allrounder 570 C type injection-molding machine with a closing force of 200 t. For this purpose a sheet die having a wall thickness of 2.5 mm with different shaped openings (some round openings with a diameter of 10 to 30 mm, some rectangular and square openings with an edge length of 10 to 30 mm) was used. Melting temperature was 280 ° C and tool temperature was 60 ° C. Mark rolron ^® 2405 and a charging time of about 2.8 seconds for the Bay Blend ^® T65 was measured. In order to leave certain areas of the film free of back-jected plastic material, a window technique process was used. To this end, when the tool was closed, the film was accurately covered with a die in the area that should be kept blank. Thus, during the back-injection, the plastic melt was successfully prevented from reaching this zone. After filling, the back-injection moldings were cooled to room temperature (23 ° C.). In all four cases (polycarbonate film with a film thickness of 150 μm, 175 μm, and 200 μm and polybutylene terephthalate blend film with a film thickness of 375 μm), bulge in the area of the film that was not post-injected Was formed.

To remove the bulge, the molding was removed from the tool and the area of the film that was not back-injected with plastic material was heated again for a short time using a commercial IR ceramic radiator and alternatively a hot-air gun. The polycarbonate film was again heated to a temperature of 175 ° C and the polybutylene terephthalate film was heated to 155 ° C. The temperature of the film was measured using a commercial line pyrometer from Bartec Methtechnic Unt Zenzorik, and the distance from the camera to the film surface was 56 cm.

The heating time was varied in the range of 0.5 to 5 seconds for the test. The final result was not different when the radiator output was low and long heating time was used, or when the output was strong and short heating time was used. After heating and cooling again, the parts did not show any earning.

Claims (15)

A) back-injecting one side of the plastic film with one or more thermoplastics, without back-injecting one or more partial regions of the plastic film,
B) cool the plastic molding obtained in step A),
C) then, at least, again heating the non-injected zone of the plastic molding obtained in step B),
Process for the production of plastic moldings. The method of claim 1, wherein the plastic film used in step A) is formed. The method according to claim 1 or 2, characterized in that the plastic film used in step A) is printed on one side. The process according to any one of claims 1 to 3, wherein at least in step C), the non-backjected zone of the plastic molding obtained in step B) is at least greater than the glass transition temperature T _g of the plastic material of the plastic film. Heating to a temperature in a region above 70 ° C. low. The process according to any one of claims 1 to 4, wherein at least in step C), the non-injected zone of the plastic molding obtained in step B) is at least greater than the glass transition temperature T _g of the plastic material of the plastic film. Heating to a temperature in the range of 50 ° C. lower and 50 ° C. higher than the glass transition temperature T _g . The process according to any one of the preceding claims, wherein at least the non-backjected zone of the plastic molding obtained in step B) is less than 20 seconds, preferably less than 15 seconds, at the temperature (s) mentioned, Particular preference is given to heating for less than 10 seconds. The method according to claim 1, wherein the plastic film has a thickness of 50 μm to 500 μm, preferably 75 μm to 400 μm, particularly preferably 100 μm to 300 μm. . The process according to claim 1, wherein the plastic film contains at least one polycarbonate or copolycarbonate. The method of claim 1, wherein the thermoplastic is at least one polycarbonate or copolycarbonate, polyacrylate or copolyacrylate, poly (meth) acrylate or copoly ( Meth) acrylate or acrylonitrile-styrene copolymer (ABS). The method according to claim 1, wherein the plastic film is transparent or translucent in at least a partial region within the non-back-jected zone. The method according to claim 1, wherein the non-back ejected area of the plastic film is covered with one or more dies or sliders in step A). 12. The method according to any one of the preceding claims, wherein the non-backjected partial region (s) of the plastic film are completely surrounded by the back-projected partial region of the plastic film. The method according to any one of claims 1 to 12, wherein in step A) no partial-continuous partial regions of the plastic film are back-injected, and partial regions of the non-back-injected plastic film are formed of the plastic film. Characterized in that it is completely surrounded by a back-injected partial region. The method according to claim 1, wherein the back-injection in step A) is carried out by a window technique. Plastic molding obtainable by the method according to claim 1.

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